The invention relates to a hydraulic rotary percussive device of the drill type, for drilling boreholes.
Drills are used for a variety of applications, such as excavating quarries, tunnels or mines.
These devices are composed of a carrying machine known as a “carrier”, on which is located a slide which holds a rotary percussive device of the drill type.
The drill generally consists of a percussion mechanism and a rotating mechanism. When the latter is installed on the carrier, it receives hydraulic power and transforms it into percussive and rotary mechanical power in order to create boreholes using a boring bar and a drilling bit in contact with the rock.
The percussion mechanism is generally rigidly mounted in the casing of the rotary percussive device whereas the rotating mechanism, comprising a motor mounted laterally on a shaft parallel to that of the percussion mechanism, rotates the shank of the boring bar by way of reduction pinions.
This shank is therefore made to rotate and receives the impacts caused by the piston of the percussion mechanism.
The drawback of this conventional solution is the high cost of the device caused by the presence of pinions which are expensive components requiring, in order to be installed in the device, costly mechanical equipment.
The document CH338419 describes a rotary percussive device comprising:                a percussion mechanism equipped with a piston able to undergo translational movement along a percussion axis and intended to strike a bit, and        a motor rotating the bit about a rotational axis more or less coinciding with the percussion axis of the piston.        
The percussion mechanism is attached to the rear surface of the motor casing.
This juxtaposition of casing and percussion mechanism gives the rotary percussive device a large size and a complex structure.
According to one embodiment, the motor is pneumatic. In this case, it is necessary for pinions to be provided. This gives the device a high cost.